Process of transforming heat



March 1, 1927. 1,619,196

- R. w. 'DAVENPORT:

PROCESS OF TRANSFORMING HEAT Filed March 12 1925 INVENTOR subject matter of said origina aratively Pa tented Me. 1, 1927.-

UNITED STATES PATENT OFFICE.-

, nansom w.;nevnnron r, or nn'rnorr,

Mario r001. company, or NEW YORK,

rnocnss or rnansronrrmc near.

MICHIGAN, Assronon 'ro cnrcaeo mu- 1:. 2., a conronarron or :nnw mnsmr. v r

c Application filed Haich 12, 1925. Serial no". 15,17a.

roved process of anical process of This invention is anim transforming heat, onmec the class known as thermodynamic cycles,

and one of its principal objects is to provide an improved art of refrigeration adapted to employ workin' substances of the type disclosed and claime in my copending application Ser. No. 603,998, filed Nov. 22,

cation is directed to the inventions original- The subject matter of the present applirefrigeration at comparatively low temperatures, thereby much improving the art in both safety and convenience, over the-old methods which require'the use of compressed gases or vapors which'a're both diificult and dangerous to use.

It is a further aim of my invention to, combine certain advantages ofrthe old cold-air refrigeration process with those ,of the old vapor time, eliminate severalof the disadvantages of both, by providing a new art of refrigeration which involves not only vaporization, compression and liquefaction, aslm the vapor cycle, but also expansion, as in the coldair cycle.

My invention also consists in a novel thermodynamic cycle which may be performed with a closerapproach to theoretical reversibility than either the reversed Clausius or Joule cycles commonly known and used heretofore, for refrigeration.

Reference will hereinafter be made to a form or forms of apparatus for carr ing out my improved process and to wor ing substances u on which my process may performed; 'ut it is to he understood that I- am neither disclosing nor claiming such machines or refrigerants in this presentapplication. Suitable machines and devices are disclosed and claimed in my co-pending application in heat en ines Ser. No. 708,936 filed Apr, 25, 1924:; of matter are set forth and claimed in the application in working. substances above identified, and the three other applications compression process and at the same.

uitable compositions hereinhcited cover, with present appli cation, a closelyfrelated series of invent1ons. '1he accompanying drawing represents, d1agrammatically, one form of apparatus in which may be'performed, in ways chosen merely for illustration, ste s of m invention. It is to the un erstoo that the ca proved process of trans in any way'confined employment of -'other form. of device or. arrangzllient of devices; nor to the heroin descri methods of using such apparatus except e the four essential definitely ormmg heat is not in so far as is defined and specified ill-rt ap'pzlalnde'd claims. j

, ermodynamic processes, to which general class of mechanical processes the present irgention belongs, all involve one or more of, the operations knownv as oompres:

ways and ing out of'mygim- 1 vto or limited. by the the herein described or any sion, condensation or liquefaction, vapori-.

zatio'n or boiling, and expansion; and m cases these operations are performed in and by certain devices such as pum engines, nozzles, workin substances. 7

volved in any gsarticular c cleor process obviously depen principal y upon the thermodynamic properties of the working substance therem employed. For example, in the old and well known reversed Joule cycle or cold-air 'refri era process, the working substance is a1 an it follows that this -=c cleinvolves but two of the above operations, namely, compression-and expansion,

since air is neither liquefied nor va orized, but remams aseous, and the sensi 1e heat only is trans ormed into kinetic ener by kinetically expandin it to produce t e .re-

frigeration. The co d-air process therefore has the disadvantage that, in order to produce refrigeration at moderately low temperatures, from 0 to 30 deg. F, for example, the volume of air handled must be ver great or else the pressures must be hig er than necessary roducing lower tern peratures than requir involving consider able thermal and mechanical losses.

On the contrary, in the old and well known reversed Clausius-Rankine cycle, or vapor compression refrigerating process, the working substance is not a gas but a liquid of low chambers, etc., upon fluids known as.

' vWhic among these operations be in- 1 liquid is fed back, warm, from p is fe boilin tem rature such as ammonia or sulphur ioxidlf whose vapor is removed at a single constant lower temperature and pressure, and which vapor is then compressed to and liquefied at a constant higher temperature and pressure. It follows that this proc ess involves but the three steps of compres sion, liquefaction and vaporization since the the higher to the lower ressure 0 ration without alfifiy expansion w atever. she source of inc cienc in this process is that the warm liquid 5 back without volume change, for a liquid cannot expand like a vapor or a gas, and hence this step is in theory and in practice, totally irreversible. But perhaps the most serious disadvantages of this process are due to certain inherent properties of liquid itself. Since all common and convenient liquids like water or alcohol have but ve low vapor pressures-.a fraction of an inc of "mercury, perhaps-at refrigerating temperatures they have never been used on a practical scale since no practical method of removing their vapor at these extremely low pressures has ever, to my knowledge, been suggested. As a consequence, li uids with practical vapor pressures at re rigerating temperatures, like ammonia, sulphur dioxide etc., have to be used notwithstanding the dis advantageously high pressures of the vapors at ordinary temperatures. Another inherent property of liquids, their tendency to supereat during evaporation, renders the old vapor compression process very ineflicient, especially with certain 1i uids.

The boilin point 0 a liquid is the temperature at w ich its vapor pressure is e ual to the total pressure to which the liqui is subjected, usually the atmospheric pressure, and a liquid begins to boil, i. e., emit bubbles of vapor, when its temperature is raised to a point at which its vapor pressure is e' ual to the, total pressure on its surface. he bubbles of vapor are always evolved at certain definite points where small gas bubbles (either evolved from' the liquid, or due to air adhering to the vessel) are present. As

theboiling proceeds, these points diminish the in number owing to the expulsion of gas, and after a time disappear a together. he tem rature then rises several degrees above ilin point withoutthe formation of bubbles. t last, however,an explosive rush of vapor is evolved, usual] in one large bubble from the bottom of t e vesel, the temperature sinking again to the boiling point,

and the process is re d. Accordin .to Aitken (1874) norma boiling occurs on y if bubbles or cavities, and hence the vapor of the liquid, are present. This result is quite general; the phase transformation proceeds normally only if both phases are present. If only one base is present, the transformation. into t eother'lags behind the change of V sion liquefaction,

temperature or pressure, and then'occurs violenty and spasmodically. In the conventional refrigerating process normal boiling is almost entirely prevents owing to the elimination of all non-condensible gas from the system, which elimi nat1on is made as complete as poss1ble,'under ticably low. Even with liquids of the type commonly used, the conventional refrigerating process secures only spasmodic boiling, and the density of the va or taken into the compressor :is'often far low that corresponding with the actual temperature of the refri erator. Furthermore, since it is impossi le to unequally heat a vessel containing liquid and vapor only, when, as is usually the case, several refrigerating temperatures are desired, all the heat has to be absorbed at the lowest temperature and vapor density with consequent inefiiciency, or a separate system operatin at a different back pressure hasto be provid ed. Y

My improved thermodynamic cycle differs essentially and basically from the processes above described.

My improved art of refrigeration may be said to consist in conducting a suitable working substance through aclosed cycle involving, successively, the vaporization, compresand ex ansion of the worrin substances While propose to set forth these four steps of my rocess separately, for the sake of greater 0 earness, it is to be understood that ,the steps need not be practised separately, and in fact may actually overlap in practice.

Referring, now, to the drawing, 1 represents a vaporizing1 chamber or boiler, containing liquid as s own, which is commonly placed in the refrigerator and connected by pipe 2 to a compressing device 3 while 4 is a condensing member and5 an expansion device, all of which when connected by pipes as shown, combine to form a closed circuit for the working substance. The space not occu ied by liquid is to be understood as being lled with the vapor of the liquid and a suitable non-condensible gas.

The carrying out of my invention may be illustrated as follows:- Upon starting the compressing device 3 which may be driven by any suitable means,the foursteps of my improved process are erformed continuously as the working su stance is caused to traverse the system, and heat is absorbed in of vapor in the latter member.

, va r.- ressure'bein a fraction of thIs fig P P a takes the former and the-condensing The mixture ofvapor and gas removed from member 1 is compressed to a hi her total pressure by the member 3, and the vapor-gas mixture leaving the member 4 is expanded in thermal the liquid in contact with the condensate formed therein, from the higher to the lower total pressure, by the expansion device 5, whence they are discharged back into boiler 1.

Assuming, for illustration, that the condenser ejects heat at a final temperature of 25 deg. G., and that it is desired to produce refrigeration at an initial temperature of 5 deg. (1., and final temperature of 5 deg. 0.,

w.th, for example, carbon tetrachloride, the vapor tension of which is only about 1 inch mercury at -5 deg. C. and about 5 inches at 25 deg. C.; and thatthe partial pressure of the non-condensible gas-air, for example, in

the condenser is about 25 inches so that the total pressure therein is about that of the s of my process atmosphere, the separate ste etail, beginning will now be set forth in. with the expansion, step.

The expansion device 5, which may be of any form, preferably of the kinetic type and assumed for illustration to be aturbine nozzle, is so arranged that, taking in the" Vapor-gas mixture from the member; at one. atmosphere total pressure, it expands 1tdown. to about 6 inches of mercury or 24 inches vacuum, meanwhile absorbing heat) from the liquid from the condenser which is brought into thermal contact with 1t, and

transforming this heat into kinetic energy' which is available to do work. The streams of liquid 1 and gas mixture total pressure of 6 inches, and the partial are as it was at the outlet of condenser 4.

The next step, the vaporizing of the liquid, ace in the boiler 1. The? continual introduc ion of the gas mixture, with the liquid, prevents the superheating which ordinarily results from the constant removal of the vapor as'in the conventional process, since new voids are constantly formed in the iiquid' by the non-condensible gas, so that the prescribed conditions for normal boiling are constantly maintained.

Owing to the peculiar principles of my invention, the point of greatest absorption of heat is at or closely adjacent the nozzle or expansion device 5. The absorption of heat continues in lesser degree as-the vapor gas mixture expands up through the liquid refrigerant in boiler 1 but at progressivelyhigher temperatures due to the-tendency of the. warmer liquid to rise and remain near the surface. This tendency toward progressively hifgher temperatures of the liquidin' a boiler o the type shown is at least in art nullified by the continuous agitation o the are then dis charged into the member 1 at the assumed liquid by the expansion of vapor and gas thereinto from expansion device 5 tendmg,

.mately constant throughout the boiler. by the compressing device 3; but when the liquid in the upper part of-the member is warmed to, for example, 5 degrees 0., the vapor pressure may rise without afiecting'the total pressure, and also without effect upon the partial vapor pressure at the entrance, which remains the same fraction of the total pressure .as before, i. e., of 6 inches or 1 inch, corresponding with -'5 deg. C. The more dense vapor corresponding. with the higher temperature is then removed from the boiler by the pump 3 since it cannot go back to the colder portion and con-dense there. In effect, the vapor pressure is increased and'the .air is expanded to a lower partial pressure during this step,- the total pressure of the mixture remaining substantially constant.

The next step. is performed by the member 3 which takes in the air-vapor mixture through pipe 2 and compresses it into the member-'4. Since the total pressure of the mixture taken in is far above the partial pressure of the vapor at, eventhe higher refrigerating temperature, this step may be conveniently and eflicient1y performed in devices which would be utterly useless in the old vapor process. In the example given, it would be necessary .to maintain a vacuum of 29 inches by the conventional process,

whichis commerciall impossible. Moreover,

sary if normal boiling ,could be maintained as in my improved process. Owing to the peculiar principles of my invention, therefore, instead of requiring a larger pump for ag1ven amount of refrigeration, the same pump will actually produce more refrigeration with my process, simply because the air, while taking up no additional s aeein the pump, has both secured a nofma vapor density and raised the total pressure. v

The final step of. my process; consists in coolingthe stream of vapor, air mixture,

preferabl progressively and graduall in the mem er 4. The .total pressure 0 the mixture discharged from the member 3 is assumed to be 1- atmosphere. -During the compressing step its temperature has necessari-1y been raised to, for example, 35 deg. (3., so that atthe beginning of the condensing step the partial vapor pressure corresponds at aiigure of about 7 inches of mercury; therefore the partial air pressure is 23 inches, and their sum is 1 atmosphere. As the stream-of mlxture passes through the member 4 it is cooled, preferably by thermal contact with a stream ofwater or air flowing in the contrary direction, so that the partial vapor. pressure is caused to gradually fall, while the total pressure remains substantially constant at 1 atmosphere. At the completion of the step, the artial vapor pressure has fallen, along witi the temperature, to about 5 inches while the air has been compressed from 23 inches to 25 inches,

by virtue ofthc peculiar principles of my invention. Meanwhile the vapor has been liquefying andvejecting heat. The liquid, and the vapor-air mixture next re-enter the expansion device, and the cycle is com lete.

It is obvious from what has been set orth, that the temperatures of refrigeration are, in my improved process of transforming heat, controlled by the total pressure in the condenser instead of by regulating the back pressure as in the vapor compression process, and thereforethe temperatures of refrigeration may be lowered by raisingthe partial air pressure in the member 4 while keeping its temperature constant. K

It will be seen that by the methods I provide, liquids of comparatively low vapor tension are made to roduce ractical refrigcrating effects, an it will lie clear that by preventing superheating of the evaporating 1i uid, by ex anding part of the working su stance an by taking in heat at the highest ossible temperature, my improved thermo ynamic cycle may closer a than sit cycles.

carried out with :1

er the Clausius-Rankine or Joule 1. The process of transforming heat, in-

volving re eatedly conducting a suitable working su stance having a gaseous incondensible component, through a closed thermodynamic cycle, which consists in succes condensing .pandmg sai sively compressing, condensing, expanding, and vaporizing the said workingsubstance.

2. The artof refrigeration consisting in compressing to ther a gas and a vapor removing heatrom saidgas and vapor and part of said vapor to liquid; ex-

gas and vapor in thermal contact with the said liquid; supplying heat to' said liquid and vaporizing it in contact with said gas;

and continuously repeating said steps in a closed cycle.

3. In the herein described art of refrigeration, the steps involving the raising of the 4 partial gas pressure and the lowering of the partial vapor pressure, consisting in bringing intocontact a body of liquid and a stream of gas-vapor mixtureand removing heat from said liquid and said mixture; and

maintaining the, said liquid and said mixture under substantially constant total pressure.

proach to theoretical reversibility 4. In the herein art of refrigthe partial pressures of a vapor-gas mixture, consistin in expanding the said mixture from a hlgher total pressure to a lower total pressure. Y

Inrthe herein described art of refrigeration, the steps involving the raising of the partial vapor pressure and the lowering of the partial air pressure. consisting in bringing into contact a body of liquid and a stream of vapor-gas mixture and supplymg heat to said liquid'and said mixture; and maintaining the said liquid and said mixture under substantially constant total pressure.

6. In the herein described art of refrigeration involving the. expanding of gas in contact with an evaporating liquid, the method of preventing superheating of the liquid consistin in releasing within the body of the said liquid a mixture of the aforesaid gas and the vapor of said liquid.

7. In the art of refrigeration involving the vaporizing of liquid to absorb heat, the

said mixture and said liquid until the partial vapor pressure'in said mixture rises to a point commensurate with a higher temperature, and then removing said mixture from contact with saidliquid, meanwhile supplying-heat to said liquid.

'8. In the art of refrigeration involving the compressing of vapor froma lower temperature and pressure to a higher tempera ture and pressure, the method of contro ling the said lower tem erature consisting in compressing a gas wlth said vapor'to a certain higher total pressure so fixed that the partial vapor pressure at the hi hertemperature bears to said higher tota ressure, a ratio commensurate with the ratio of the partial vapor press?! at the desired lower temperature to the desired lower total pressure and then maintaining said higher and lower total pressures.

9. In the art of refrigeration involving themixing of liquid from a condenser also containin a. non-condensible gas, with li uid'alrea y in the refrigerator, thetmeth of cooling said mixing, consisting inkinetically expandin the said non-condensible gas in therma contact with said liquid fromTLhe condenser.

10. In a closed 0 cle stem containin as y 8y {En 125 a working substance a quantity of which is liquid at ordinary temperaturesand pressures and a gascousfluid substantially inert to and insoluble in said li uid so that the total pressure on the liqui is in excess of its own vapor pressure, the therthe first named liquid prior to modynamic process which comprises cireulatingx the' mixed gas and vs orof the liquid 1: rough the system, and orcin the mixed gas and vapo during each eye e of its movement to pass thpough a body of said liquid.

,inert to and insoluble in said li of its own vapor pressure,

11. In a closed cycle system c'ontainirfig as uid a working substance a quantity of which is liquid at ordinary temperatures and pressures and a gaseous fluid substantially quid so that the total pressure on the liquid is in excess the thermodynamic process which comprises circulating the mixed gas and vapor of the liquid through the system, and expanding the mixed gas and vapor during each cycle of its rlpoueiment in contact. with a body of the m 12.. The process of producing refrigeration which comprises repeatedly conducting a suitable working substance through a thermodynamic cycle having a higher ressure part and a lower pressure art, an maintaining the pressure in the rst named part substantially at one atmosphere absolute.

13. The process of producing refrigeration which comprises repeatedly conducting a suitable workin substance through a t ermodynamic cyc e having a higher pressure part and a lower pressure part, and maintaining the pressure in the second named part below ten inches absolute of mercury and the pressure of said first named part at substantially one atmosphere absolute.

'14. The process of producing refrigeration which com risesre eatedly conducting a suitable wor in su tan'ce through a thermodynamic cyc e having a higher presv in said sure part and a lower pressure part, and maintaining the difi'erence in the pressures arts at less than one atmosphere. 15. The process of tion which com rises repeatedly conducting a suitable wor in en stance through a thermodynamic cyc e having a higher pressure part and a lower pressure part, and

.in said vapor of t through a thermodynamic, c c

maintaining the difference in the pressures parts at substantially twenty-si inches absolute of mercury.-

16. In the process of roducing refrigeration by the use of a wor ing substance comprisin a liquid and a gas substantlally inert to an inso uble in said liquid, the step of expandin a' stream of gas, liquid and the in which a conducted 0 having a bi her ressure part where eat is ejected e15 a owe pressure part where heat is absorbed, the process of refrigeration which 17. In a system of the type working substance is repeatedl stance changes state and producing .refrigera- I e liquid into a body of the liquid.

comprises utilizing a suitable gas-vapor mixture as the workm substance, and main- .tainingthe sum of t e partial gas and vapor pressuresin the higher pressure part of the system at substantially one atmosphere absolute.

18. In a working substance is repeatedl conducted through a thermodynamic cyc e having a higher pressurepart where heat is ejected and a absorbed, theprocess of refrigeration which comprises utilizing a suitable gas-vapor mixture as the working substance, andymaintaining the sum of the partial gas and vapor pressures in the lower pressure part of the system at less than ten inches absolute of mercury.

19. In a system of the type in which a working substance is repeatedl conducted through athermodynamic cyc ehaving a higher ressure part where heat is ejected and a ower pressure part where heat is absorbed, the process of refrigeration which ower pressure part where heat is system of thetype in which a comprises utihzing a suitable gas-vapor mixture'as the working substance, and maintaining the difference between the sums of the partial as and vapor pressures in the higher and in t e lower pressure parts of the system at substantially one atmos here.

20. The process of re 'geration which comprises circulating a suitable working substance through a closed cycle having a higher pressure part where the working subgives up heat and a lower pressure part where the working substances changes state and absorbs heat, and controlling the operating pressures of the high and low pressure parts of the cycle and lower pressure parts of the cycle so as to produce a predetermined low temperature in the lower pressure part of the cycle regardless of the temperature of the higher pressure part of the cycle by fixing and maintaining the ratios of the partial pressures of the incondensible coin nent to the total pressures of the parts 0 the c cle.

RAN OM W. DA NPORT. 

